In a high capacity primary or secondary cell, the active material of at least one of the electrodes is selected from transition metal oxides or their (partially) lithiated forms, such as TiO2, Nb2O5, HfO2, MnO2, LiyNiO2, LiyCo2, Ldy(NiCo)O2, or LiyMn2O4, in the form of electrically interconnected nanocrystalline particles of 1-250 nm. size. Pref. the particles are mixed with graphite and a binder, e.g. ethylene-propylene-diene monomer or PTFE, and compressed to form the electrode.